(a) Field of the Invention
The present invention relates to a thin film transistor array panel and a method of manufacturing the same.
(b) Description of the Related Art
A flat panel display, such as a liquid crystal display (“LCD”), an organic light emitting diode (“OLED”) display and an electrophoretic display, generally includes a plurality of pairs of field generating electrodes and an electro-optical active layer interposed between the field generating electrodes.
In general, one of a pair of field generating electrodes is connected to a switching element so as to be applied with electrical signals, and an electro-optical active layer converts the electrical signals into optical signals to display an image.
An LCD includes a liquid crystal layer as the electro-optical active layer, and OLED display includes an organic light emitting layer as an electro-optical active layer.
A flat panel display includes thin film transistors (“TFTs”) being three-terminal switching elements, gate lines transmitting scanning signals for controlling the thin film transistors, and data lines transmitting signals to be applied to pixel electrodes.
Each TFT includes a thin film formed of an amorphous semiconductor or a polycrystalline semiconductor.
The amorphous semiconductor thin film can be applied to a display device which has a substrate formed of glass having a low melting point or plastic, since the amorphous semiconductor thin film can be formed at a low temperature. However, an amorphous semiconductor thin film has low field effect mobility, which hinders the TFT from increasing its operation speed. Further, a photo leakage of an amorphous semiconductor thin film current is high, which causes unstable characteristics of the TFT.
On the contrary, the polycrystalline semiconductor thin film has high field effect mobility and optical stability.
Meanwhile, forming the polycrystalline semiconductor thin film requires a process of crystallizing a semiconductor on a substrate. In this respect, a top gate structure is used. In this case, however, the structure of the TFT and the process thereof become complex, and manufacturing cost is significantly increased.